I²C

Device tree

Download and compile the example Inter-Integrated Circuit (I²C) device tree file imx53-usbarmory-i2c.dts.

Also ensure that i2c support is enabled in the kernel configuration, otherwise you can recompile the kernel with the latest configuration usbarmory_linux-4.14.config.

The example device tree enables this I²C configuration on the pin header:

pin	Mk I
1	Ground
2	USB 5V
3	SDA
4	SCL
5	GPIO5[28]
6	GPIO5[29]
7	GPIO5[30]

I²C EEPROM

Once the i2c-dev kernel module is loaded, it is possible to access the I²C device via character device /dev/i2c-0 using userland tools such as i2c-tools or, in case of an EEPROM device, a modified verision of eeprog.

The following example shows detection, read and write operations on the Microchip 24LC16B EEPROM.

# apt-get install i2c-tools
# modprobe i2c-dev
# i2cdetect 0
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-0.
I will probe address range 0x03-0x77.
Continue? [Y/n]
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 51 52 53 54 55 56 57 -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

# eeprog /dev/i2c-0 0x50 -fxr 0:32
eeprog 0.7.6-tear12, a 24Cxx EEPROM reader/writer
Copyright (c) 2003-2004 by Stefano Barbato - All rights reserved.
Copyright (c) 2011 by Kris Rusocki - All rights reserved.
  Bus: /dev/i2c-0, Address: 0x50, Mode: 8bit
  Operation: read 32 bytes from offset 0, Output file: <stdout>
  Reading 32 bytes from 0x0

 0000|  ff ff ff ff ff ff ff ff   ff ff ff ff ff ff ff ff
 0010|  ff ff ff ff ff ff ff ff   ff ff ff ff ff ff ff ff

# echo -n "USB armory" | ./eeprog /dev/i2c-0 0x50 -w 0 -f -t 5
eeprog 0.7.6-tear12, a 24Cxx EEPROM reader/writer
Copyright (c) 2003-2004 by Stefano Barbato - All rights reserved.
Copyright (c) 2011 by Kris Rusocki - All rights reserved.
  Bus: /dev/i2c-0, Address: 0x50, Mode: 8bit
  Operation: write at offset 0, Input file: <stdin>
  Write cycle time: 5 milliseconds
  Writing <stdin> starting at address 0x0
..........

# eeprog /dev/i2c-0 0x50 -fxr 0:32
eeprog 0.7.6-tear12, a 24Cxx EEPROM reader/writer
Copyright (c) 2003-2004 by Stefano Barbato - All rights reserved.
Copyright (c) 2011 by Kris Rusocki - All rights reserved.
  Bus: /dev/i2c-0, Address: 0x50, Mode: 8bit
  Operation: read 32 bytes from offset 0, Output file: <stdout>
  Reading 32 bytes from 0x0

 0000|  55 53 42 20 61 72 6d 6f   72 79 ff ff ff ff ff ff
 0010|  ff ff ff ff ff ff ff ff   ff ff ff ff ff ff ff ff